1. Field of the Invention
The present invention relates to a circuit board packaging structure and, more particularly to a circuit board packaging structure in switching equipment.
2. Description of the Related Art
In recent years, there has been offered a variety of communications systems utilizing optical cables each composed of an optical fiber exhibiting a high transmission efficiency. For example, a circuit transmission line may be formed by use of the optical cables in Broadband-ISDN system, such as asynchronous transfer mode (ATM) switching equipment and also in an integrated services digital network (ISDN) network. Accordingly, the ATM switching equipment includes a photoelectric converting portion for converting a transmitted optical signal into an electrical signal and converting the electrical signal into the optical signal when transmitting the electrical signal to a circuit transmission line. Then, the optical cable is connected via an optical connector to the photoelectric converting portion. Hereinafter, a configuration having the above optical connector and the photoelectric converting portion is termed as an optical module.
When the thus structured optical modules are mounted in a box body of the switching equipment, according to the prior art construction, the optical connectors are disposed together with the photoelectric converting portions inwardly of the board in the box body. With this arrangement, the optical cables have to be connected to the optical connectors by perforating the board and guiding the optical cables therethrough. That is, the connector normally has a male connector connected to the end of the optical cable and a female connector connected to the photoelectric converting portion. These male and female connectors are disposed together inwardly of the board, and hence the optical cable has to penetrate the board.
Further, according to a packaging structure of a circuit in an electric mechanical apparatus, there may be a case in which packaging involves dividing one circuit into a plurality of modules, individually mounting these modules on separate circuit boards and, at the same time, connecting these circuit boards to each other. In this case, a plurality of circuit boards are connected perpendicularly to one sheet of circuit board (Back Wiring Board (hereinafter abbreviated to [BWB]) so that the plurality of circuit boards are parallel to each other. This construction is known as a bookshelf construction.
A transmission line corresponding unit of the switching equipment needs one optical module per subscriber""s transmission line. It is necessary for the board to be perforated by two holes because photoelectric connections must be made to two lines of optical cables within one optical module. Then, normally in the switching equipment, the board has to be perforated with a total of sixteen holes in order to accommodate eight subscriber transmission lines.
Thus, when the number of holes increases, the strength of the board decreases, possibly resulting in the board becoming warped. Further, a large plurality of wires must be arranged on the board. Problems may arise due to the presence of the holes which hinder the degree of freedom in the wiring design. In addition, this contributes to a reduction in the area capable of accommodating wires and to a decline in wire accommodatability.
It is a first object of the present invention to provide a circuit board packaging structure that does not require perforating a board with holes, that provides a degree of freedom for wiring design on the board and prevents a decline in wire accommodatability in equipment using such optical modules.
Further, in the case of adopting the above-mentioned bookshelf construction, a problem arises as to how to apply cooling air for cooling circuit elements on each circuit board in order to improve a cooling efficiency. In particular, if high exothermic elements (e.g., LSIs, etc.) are contained in the circuit elements, a decision must be made as to which circuit board should be used for mounting these high exothermic elements and how to expose them to the cooling air.
It is a second object of the present invention to provide a circuit board packaging structure capable of obviating the above problem, when packaging an electric circuit on a circuit board based on the bookshelf construction, and positively cooling off circuit elements exhibiting a comparatively high exothermic quality.
Also, in the case of using the above bookshelf construction, if an element requiring maintenance and inspection is contained in the circuit elements, there are problems which follow. That is, when opening a door of the electric mechanical apparatus and exposing the circuit board to the outside, maintenance and inspection purposes, a large quantity of cooling air will flow out of this opened door so that not enough cooling air will circulate along the peripheries of the circuit elements except for this element. Thus, during the maintenance and inspection of some elements, other circuit elements will not be sufficiently cooled off. Hence, even if some circuit elements are usable, this electric mechanical apparatus as a whole may be brought into an inoperable state.
It is a third object of the present invention to provide a circuit board packaging structure that is capable of obviating the above problem and performing the maintenance and inspection of some circuit elements without influencing the cooling air flowing to other elements.
Moreover, up until now the above bookshelf construction has not been proposed for ATM switching equipment. Accordingly, in the conventional switching equipment, the circuits are packaged on a single circuit board or on a plurality of circuit boards arranged in parallel. By the way, in ATM switching equipment, a transmission line corresponding unit for accommodating transmission lines extending from subscriber""s terminals or junction transmission lines from other switching equipment includes firmware exhibiting a function only selectively utilized. In the case of the conventional circuit board, however, it is impossible to eliminate the firmware having the function which is not utilized. Hence, with respect to all the transmission line corresponding units, all kinds of firmware have to be packaged irrespective of whether or not the functions thereof are utilized. For this reason, the equipment increases in size on the whole, and, at the same time, the dissipation of electric power unnecessarily increases.
It is a fourth object of the present invention to provide a circuit board packaging structure that is capable of obviating the above problem and easily eliminating the firmware having the non-utilized function out of the transmission line corresponding unit of the ATM switching equipment.
According to the present invention, the following constructions and elements are taken for obviating the respective problems given above.
According to a first aspect of the present invention, there is provided a construction for obviating the first problem described above. That is, there is provided a circuit board packaging structure, comprising: an optical cable; an optical module having a photoelectric converting portion connected to the optical cable; and a circuit board including an electric circuit unit in an internal portion thereof. The optical cable and the optical module are disposed on an external portion of the circuit board. The electric circuit unit provided on the internal portion of the circuit board and the optical module are electrically connected to each other through an electric conductor traversing the circuit board.
According to a second aspect of the present invention, there is provided a construction for obviating the second problem given above. That is, there is provided a circuit board packaging structure, comprising: a plurality of circuit boards each packaged with electric circuit parts and disposed parallel to each other. The circuit board packaged with the electric circuit parts exhibiting a larger exothermic quantity than those of the electric circuit parts packaged on the other circuit boards is disposed outermost among the plurality of circuit boards and, at the same time, disposed so that the surface packaged with the electric circuit parts exhibiting the larger exothermic quantity is directed outside.
According to a third aspect of the present invention, there is provided a construction for obviating the third problem given above. That is, there is provided a circuit board packaging structure, comprising: first circuit boards each packaged with electric circuit parts and disposed parallel to each other; a second circuit board connected perpendicularly to the plurality of first circuit boards and packaged with the electric circuit parts; a first air duct for flowing cooling air for the electric circuit parts along the first circuit boards; a second air duct for flowing cooling air for the electric circuit parts along the surface of the second circuit board; and a diverting element for diverting some cooling air flowing within the first air duct into the second air duct by making the first air duct communicate with the second air duct in an adjustable manner.
According to a fourth aspect of the present invention, there is provided a construction for obviating the fourth problem given above. That is, there is provided a packaging structure of a circuit board for packaging a transmission line corresponding unit, of an ATM switching equipment, for accommodating a plurality of transmission lines and, at the same time, processing the data from each transmission line on a cell-basis, the packaging structure comprising: a first circuit board packaged with electric circuit parts for executing an indispensable service among the respective electric circuit parts constituting the transmission line corresponding unit; and a second circuit board adapted to be attached to the first circuit board when desired and, at the same time, packaged with electric circuit parts for executing an arbitrary additional service among the respective electric circuit parts.
According to the first aspect of the present invention, it is enough to make electric connections only by use of the electric conductors in portions where the upper and lower surfaces of the board are connected to each other, and hence there is eliminated the necessity for perforating the board with through-holes for the optical cables.
Also according to the first aspect of the present invention, the packaging structure of the circuit board is widely utilizable in a variety of equipments using the optical cables. This is especially useful in a switching equipment employed in a communications network utilizing the optical cables.
For example, when the present invention is applied to an ATM switching equipment, it follows that the above electric circuit unit is a transmission line corresponding unit for accommodating a plurality of transmission lines and, at the same time, processing the data from each transmission line on the cell-basis.
Herein, the board is provided with a connector to which the optical module can be removably attached. With this arrangement, the optical module can be readily replaced.
This connector may involve the use of a penetration type connector penetrating the board and a non-penetration type connector which does not penetrate the board. When using the non-penetration type connector, it is possible to prevent a decrease in the strength of the board.
Further, the above-stated connector is constructed including a holding wall surrounding a part of the optical module. This construction makes it possible to enhance the connecting strength of the optical module.
When a shield film is provided in at least one of the interior and the exterior of the connector, electric disturbance to the optical module can be prevented.
Also, the board normally has a ground. An electric potential of this ground is, however, preferably equalized to an electric potential of the above connector and a ground potential of the electric circuit packaged on the board. This can prevent a mistake in terms of logic of a digital circuit.
The transmission line corresponding unit is separated into individual units, individually connected to the plurality of transmission lines accommodated therein, for individually processing the cells and the common unit, connected to each of the individual units, for batch-processing the cells processed by the respective individual units. The individual units and the common unit can be thereby separately packaged, and, therefore, the packaging can be rationalized, resulting in a more desirable mode for the packaging structure.
Herein, there can be considered a mode which follows. The common unit is packaged on the board, and the individual units are packaged on the plurality of individual unit oriented boards prepared corresponding to the individual units. These individual unit oriented boards are attached to the above circuit board. The individual units are connected to the respective terminals via the optical cables by means of the optical modules provided on the external portion of the circuit board and, at the same time, electrically connected to the common unit. In this mode, the plurality of individual unit oriented boards packaged with the individual units are connected perpendicularly to the circuit board but arranged parallel to each other. This arrangement makes for neat packaging and facilitates assembly.
Moreover, the common unit oriented connector is provided on the circuit board, and, simultaneously, the auxiliary board is adapted to be attached to this common unit oriented connector. The auxiliary board is thereby parallel to and spaced at a fixed distance from the circuit board. It can also be considered packaged with the common unit. Based on such a structure, the auxiliary board is simply removed, and the common unit can be easily replaced and repaired. Furthermore, the auxiliary board is separated from the circuit board by means of the connector, and it is therefore feasible to increase the cooling efficiency of the common unit mounted on the auxiliary board.
In this case, the common unit is provided on the inner side of the auxiliary board, i.e., on the side of the circuit board. In addition, the radiating fins for radiating the heat from the common unit are provided on the outer side of the auxiliary board, thereby further enhancing the cooling efficiency.
Also, two connectors of the type described above are mounted in parallel on the circuit board. When forming a heat radiating path defined by the two connectors, the circuit board and the auxiliary board, this heat radiating path serves as a path for air flow, whereby the cooling efficiency can be increased.
Moreover, when the circuit board is equipped with an air blow guide constituting an air blow path with respect to the circuit board so as to externally surround the auxiliary board, the air flows through this air blow path, whereby the cooling efficiency can be increased. In this arrangement, cooling fans may be provided for forcibly blowing air to the air blow path.
Note that the ATM switching equipment includes a switch connected to the common unit of the transmission line corresponding unit. Then, when having the switch-side optical module as an interface for connecting the common unit to the switch, the transmission line-side optical module is packaged on the central proton of the circuit board, while the switch-side optical module is packaged on the peripheral portion of the circuit board. The packaging structure can be thus rationalized.
By the way, the common unit is not packaged on the circuit board but on the common unit oriented board. The individual units are packaged on the plurality of individual unit oriented boards prepared according to the individual units. This common unit oriented board and the individual unit oriented boards can also be mounted on the circuit board. In such case, the individual units are connected to the respective terminals via the optical cables through an intermediary of the optical modules provided on the external portion of the circuit board and, at the same time electrically connected to the common unit.
In this arrangement, the common unit oriented board packaged with the common unit and the plurality of individual unit oriented boards packaged with the individual units are connected perpendicularly to the circuit board and arranged parallel to each other. This arrangement is preferable in terms of facilitating assembly.
Note that the common unit may be, when packaging the common unit, divided into a plurality of common subunits and then packaged. This is, however, done only if the number of the subunits is smaller than the number of individual units.
Further, according to the second aspect of the present invention, the electric circuit parts generating more heat than those of the electric circuit parts packaged on other circuit boards can be disposed on the outer surface of the circuit board. Hence, these electric circuit parts can be subjected to more concentrated cooling.
For instance, the electric circuit parts can be cooled off by providing cooling fans for blowing the cooling air against the electric circuit parts having the larger exothermic quantity.
Particularly, for cooling off the electric circuit parts packaged on the plurality of circuit boards, first cooling fans are provided for blowing the cooling air along the plurality of circuit boards. The cooling air from the first cooling fans acts to cool off the electric circuit parts having the larger exothermic quantity. Second cooling fans are provided for blowing cooling air against the outwardly disposed circuit boards from the perpendicular direction. Thereby, the electric circuit parts exhibiting the larger exothermic quantity can be cooled off, even though the cooling air is brought in from outside through a common inlet.
The above electric circuit parts may be those constituting the transmission line corresponding unit, of the ATM switching equipment, for accommodating the plurality of transmission lines and, at the same time, processing the data from each transmission line. This electric circuit unit is separated into a plurality of individual units, individually connected to the plurality of transmission lines, for individually processing the cells and the common unit for batch-processing the cells processed by the individual units. Simultaneously, when the thus separated individual units or common unit are packaged on the separate circuit board, cooling can be attained corresponding to the difference in the exothermic quantity caused by the difference in the air throughput. An example of this packet is an ATM cell which is a fixed length cell.
That is, if the electric circuit parts having the larger exothermic quantity are those constituting the common unit, cooling of this common unit can be concentrated thereon.
There may be prepared two such common units having the same configuration for the active and standby systems. If constructed in this way, the common unit can be maintained and replaced during the operation of the transmission line corresponding unit.
When constructed to respectively package these two common units on separate circuit boards, the circuit boards packaged with the common units may be disposed at both ends of the plurality of circuit boards. Even if thus arranged, since there are two circuit boards facing outside, among the plurality of circuit boards, effective cooling can be attained.
The plurality of such circuit boards are connected to the same connecting board, and the wires for connecting the common units to the individual units are arranged on the outer surface of this connecting board. With this arrangement, the plurality of individual units can be easily connected to the plurality of common units.
The circuit boards packaged with the common units are connected to the connecting board in a symmetrical manner about the axis orthogonal to the connecting board. At the same time, the wires for connecting the respective common units to the plurality of individual units are provided on the outer surface of the connecting board in a rotationally symmetrical manner about the axis, corresponding to the respective common units. Thus, the two sheets of circuit boards packaged with the common units can be identical to each other.
Further, a circuit board packaging structure, comprises a plurality of first rectangular circuit boards each packaged with electric circuit parts and disposed parallel to each other. This packaging structure also comprises a second circuit board packaged with the electric circuit parts and disposed in a direction orthogonal to respective sides of the plurality of first circuit boards. The plurality of first circuit boards are electrically connected to the second circuit board. With this arrangement, the respective circuit boards can be connected to each other while avoiding complicated wiring.
In this case, the packaging structure further comprising a cooling fan for flowing cooling air along the second circuit board. Even when the second circuit board is packaged with the electric circuit parts exhibiting the larger exothermic quantity, the electric circuit parts can thereby be cooled off with a high efficiency.
In this case, the electric circuit parts constituting the individual unit are packaged on the first circuit board for every individual unit. The electric circuit parts constituting the common unit can be packaged on the second circuit board. If constructed in this way, the common unit can be easily electrically connected to the plurality of individual units.
A plurality of second circuit boards are provided, and the two active and standby system common units each having the same construction are respectively packaged on these second circuit boards. It is therefore possible to carry out the connections between the respective common units and the plurality of individual units with a simple construction even when the two common units are prepared.
The packaging structure further comprises a partitioning plate for partitioning the second circuit board packaged with the active system common unit and the second circuit board packaged with the standby system common unit. Cooling fans are provided for two systems and independently cool off the second circuit boards partitioned by the partitioning plate. With this construction, when one common unit is maintained and inspected, cooling of the other common unit can continue. Hence, there is no necessity for stopping all of the transmission line corresponding units.
According to the third aspect of the present invention, the cooling air flowing through a first air duct cools off the electric circuit parts packaged on the first circuit boards. At the same time, this cooling air can be diverted to a second air duct by a diverting element. Therefore, the electric circuit parts package on the surface of the second circuit board can be cooled off. Further, when maintaining and inspecting the electric circuit parts packaged on the second circuit board, the diverting element can shut off a portion between the first and second air ducts, whereby the electric circuit parts on the second circuit board can be exposed to the outside without preventing the electric circuit parts on the first circuit boards from being cooled off by the cooling air flowing through the first air duct.
In this case, the diverting element opens and closes an opening formed in the first air duct using hinges. At the same time, the diverting element has a movable plate which is brought into contact with a proximal edge portion of the second air duct when opening the first air duct and a bellows for covering an area between the movable plate and a portion exclusive of locations in which the hinges are provided in the periphery of the opening. The diverting element can be thereby simply constructed.
Further, the second air duct is formed with an adjustable opening for exposing the electric circuit parts packaged on the second circuit board to the outside. When constructed in this way, the electric circuit parts can easily be maintained and inspected.
This opening of the second air duct is constructed to be opened and closed by a cover in the form of a transparent plate. The electric circuit parts can thereby be visually inspected even when the opening is closed.
According to the fourth aspect of the present invention, the first circuit board is packaged with only the electric circuit parts for executing an indispensable service among the electric circuit parts constituting the transmission line corresponding units of an ATM switching equipment. The second circuit board adapted to be attached to the first circuit board is packaged with the electric circuit parts for executing other arbitrary additional services. Hence, when the service of the electric circuit parts packaged on this second circuit board is not needed, this second circuit board can be eliminated. That is, the transmission line corresponding unit can be constructed of only the irreducible minimum number of electric circuit parts by removing the unnecessary electric circuit parts per individual transmission line.